As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TACHOMETER FULL SCALE DEFLECTION ON ANALOG NEEDLE WHEN POWER SELECTED AND LOW ANALOG READING ON EGT. PROBLEM TRACED TO ROUTING OF BOTH CABLES THROUGH A FIRESLEEVE OVER THE TURBOCHARGER. THE FIRESLEEVE HAS BUNED AWAY, LOSING ITS FIRE RESISTANT QUALITIES AND CAUSING BOTH TACHO AND EGT CABLES TO MELT. PROBABLY SATISFACORY ON AN AIR COOLED ENGINE, BUT NOT ON A CLOSE COWLED, WATER COOLED ENGINE.